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We use this safety relay to ensure our drive is disconnected from a motor when a robot changes from one motor to another of our system. We routinely break the connections between S11-S12 and S21-S22. Upon re-connecting a motor we use the
trailing edge of connection S33-Y2. Our problem is that occasionally we have to shut the robot motors off before the safety relay will reset (trailing edge of connection S33-Y2), and sometimes just cycling the connections S11-S12 S21-S22, then re-asserting the trailing edge of connection S33-Y2 will get us going again. Has anyone else experienced this situation or suggest what to look for?

Tim, we had something similar with a Pilz PNOZ XM1 safety relay. It's microprocessor based, and the noise from the contactors was tripping occasionally, ie the unit wont reset. tech support suggested some surge supressors (either RC or MOV) on all of the contactors, and that's fixed the problem.

Thanx Mark,
All of the contactors within our own panel have suppression. I believe the cell panel is also protected by suppressors, but I am not
certain. This would be a good thing for our techs to verify.

I have had this problem with the Pilz PNOZ XV2, which is the Pilz equivalent of this relay. The two channels must break together within a specified time, otherwise the relay thinks there is a fault in the E stop field devices. Re-setting and breaking the loop to clear this fault, indicates that a device may have a contact that is a bit slower to break than its companion on the other channel.

Thanx Neil,
We thought this may be happening so we jumpered the cable that went to the cell panel. This worked very well, we had no problems. We then reconnected the cable to the cell panel and jumpered the relay contacts inside the panel. The problem came back. Appearantly we are picking up some noise from inside the cell panel, but I am not sure how we can prove it.

The principle of operation of any dual channel Safety Relay is that both channels S11- S12, S21-S22 make and break together. There is a simultaneity time between both channels. If the relay is energised and one channel is broken the relay will de-energise, if you try to reset then the relay will not because it has not seen both channels break. This is a requirement of EN954 CAT 3 and 4. It detects a single fault in the system. If this were not the case then in the future if the second contact failed then the E Stop would be useless. It is not a problem with the relay but with the application.

Best regards

Brian Maher
Applications & Technical Support Engineer

PILZ Ireland Industrial Automation,
Business & Technology Park, Model Farm Road, Cork, Ireland.
Telephone +353 (021) 4804-977, Fax +353 (021) 4804-994
E-Mail: mailto:b.maher@pilz.ie, Internet: http://www.pilz.com

Hi Brian,
I have had a problem with a Telemecanique Safety relay, and whilst browsing the web, searching for inspiration, I came across your posting.

I just wanted to say, many thanks for your lucid, operation description, you saved me an awful lot of time on a wild goose chase.

Thanks again,

Best Regards,
Norm.
(Australia)